


void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    // Normalized pixel coordinates (from 0 to 1)
    vec2 uv = (2. * fragCoord - iResolution.xy ) / min(iResolution.xx, iResolution.yy);

    // Time varying pixel color
    vec3 col = vec3(0., 0., 0.);
    if(length(uv) < 1.) {
         col = vec3(1, 1, 1);
    }

    // Output to screen
    fragColor = vec4(col,1.0);
}